2001 INFINITI QX4 engine

On Board Diagnosis LogicNBEC0356Malfunction is detected when vacuum cut valve bypass valve does
not operate properly.
Possible CauseNBEC0593IVacuum cut valve bypass valve
IVacuum cut valve
IBypass hoses for clogging
IEVAP control system pressure sensor and circuit
IEVAP canister vent control valve
IHose between fuel tank and vacuum cut valve clogged
IHose between vacuum cut valve and EVAP canister clogged
IEVAP canister
IEVAP purge port of fuel tank for clogging
SEF210Y
SEF211Y
SEF239Y
DTC Confirmation ProcedureNBEC0357CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
TESTING CONDITION:
For best results, perform test at a temperature of 5 to 30ÉC (41
to 86ÉF).
WITH CONSULT-IINBEC0357S011) Turn ignition switch ªONº.
2) Start engine and warm it up to normal operating temperature.
3) Turn ignition switch ªOFFº and wait at least 10 seconds.
4) Start engine and let it idle for at least 70 seconds.
5) Select ªVC CUT/V BP/V P1491º of ªEVAPORATIVE SYSTEMº
in ªDTC WORK SUPPORTº mode with CONSULT-II.
6) Touch ªSTARTº.
7) When the following conditions are met, ªTESTINGº will be dis-
played on the CONSULT-II screen. Maintain the conditions
continuously until ªTESTINGº changes to ªCOMPLETEDº. (It
will take at least 30 seconds.)
ENG SPEED Idle speed or more
Selector lever Suitable position
Vehicle speed 37 km/h (23 MPH) or more
B/FUEL SCHDL 1.3 - 10 msec
If ªTESTINGº is not displayed after 5 minutes, retry from
step 3.
8) Make sure that ªOKº is displayed after touching ªSELF-DIAG
DTC P1491 VACUUM CUT VALVE BYPASS VALVE
On Board Diagnosis Logic
EC-592

Component DescriptionNBEC0361The malfunction information related to A/T (Automatic Transmission) is transferred through the line (circuit)
from TCM (Transmission control module) to ECM. Therefore, be sure to erase the malfunction information such
as DTC not only in TCM (Transmission control module) but also ECM after the A/T related repair.
On Board Diagnosis LogicNBEC0363Malfunction is detected when an incorrect signal from TCM (Trans-
mission control module) is sent to ECM.
Possible CauseNBEC0594IHarness or connectors
[The communication line circuit between ECM and TCM
(Transmission control module) is open or shorted.]
IDead (Weak) battery
ITCM (Transmission control module)
SEF058Y
DTC Confirmation ProcedureNBEC0364NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
TESTING CONDITION:
Before performing the following procedure, confirm that bat-
tery voltage is more than 10.5V at idle.
WITH CONSULT-IINBEC0364S011) Turn ignition switch ªONº.
2) Select ªDATA MONITORº mode with CONSULT-II.
3) Start engine and wait at least 40 seconds.
4) If 1st trip DTC is detected, go to ªDTC P0600 A/T COMMUNI-
CATION LINE Diagnostic Procedureº, EC-443.
WITH GSTNBEC0364S02Follow the procedure ªWITH CONSULT-IIº above.
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DTC P1605 A/T DIAGNOSIS COMMUNICATION LINE
Component Description
EC-603

AEC877A
Component DescriptionNBEC0367When the gear position is ªPº (A/T models only) or ªNº, park/neutral
position (PNP) switch is ªONº.
ECM detects the position because the continuity of the line (the
ªONº signal) exists.
For A/T models, the park/neutral position (PNP) switch assembly
also includes a transmission range switch to detect selector lever
position.
CONSULT-II Reference Value in Data Monitor
Mode
NBEC0368Specification data are reference values.
MONITOR ITEM CONDITION SPECIFICATION
P/N POSI SWIIgnition switch: ONShift lever: ªPº or ªNº ON
Except above OFF
ECM Terminals and Reference ValueNBEC0683Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
44 L PNP switch[Ignition switch ªONº]
IGear position is ªPº or ªNº (A/T models).Approximately 0V
[Ignition switch ªONº]
IExcept the above gear positionBATTERY VOLTAGE
(11 - 14V)
On Board Diagnosis LogicNBEC0370Malfunction is detected when the signal of the park/neutral position
(PNP) switch is not changed in the process of engine starting and
driving.
Possible CauseNBEC0595IHarness or connectors
[The park/neutral position (PNP) switch circuit is open or
shorted.]
IPark/neutral position (PNP) switch
DTC P1706 PARK/NEUTRAL POSITION (PNP) SWITCH
Component Description
EC-604

DTC Confirmation ProcedureNBEC0371CAUTION:
Always drive vehicle at a safe speed.
NOTE:
If ªDTC Confirmation Procedureº has been previously conducted,
always turn ignition switch ªOFFº and wait at least 10 seconds
before conducting the next test.
SEF212Y
SEF213Y
WITH CONSULT-IINBEC0371S011) Turn ignition switch ªONº.
2) Select ªP/N POSI SWº in ªDATA MONITORº mode with CON-
SULT-II. Then check the ªP/N POSI SWº signal under the fol-
lowing conditions.
Position (Selector lever) Known-good signal
ªNº and ªPº position ON
Except the above position OFF
If NG, go to ªDiagnostic Procedureº, EC-608.
If OK, go to following step.
3) Select ªDATA MONITORº mode with CONSULT-II.
4) Start engine and warm it up to normal operating temperature.
5) Maintain the following conditions for at least 60 consecutive
seconds.
ENG SPEED 1,500 - 2,500 rpm
COOLAN TEMP/S More than 70ÉC (158ÉF)
B/FUEL SCHDL 3.6 - 12 msec
VHCL SPEED SE 70 - 100 km/h (43 - 62 MPH)
Selector lever Suitable position
6) If 1st trip DTC is detected, go to ªDiagnostic Procedureº,
EC-608.
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DTC P1706 PARK/NEUTRAL POSITION (PNP) SWITCH
DTC Confirmation Procedure
EC-605

Diagnostic ProcedureNBEC0374
1 CHECK PNP SWITCH GROUND CIRCUIT FOR OPEN AND SHORT
1. Turn ignition switch ªOFFº.
2. Disconnect park/neutral position (PNP) switch harness connector.
SEF011SA
3. Check harness continuity between PNP switch terminal 1 and engine ground. Refer to Wiring Diagram.
Continuity should exist.
4. Also check harness for short to power.
OK or NG
OK©GO TO 3.
NG©GO TO 2.
2 DETECT MALFUNCTIONING PART
Check harness for open or short between park/neutral position (PNP) switch and engine ground.
©Repair open circuit or short to power in harness or connectors.
3 CHECK PNP SWITCH INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT
1. Disconnect ECM harness connector.
2. Check harness continuity between ECM terminal 44 and PNP switch terminal 2. Refer to Wiring Diagram.
Continuity should exist.
3. Also check harness for short to ground and short to power.
OK or NG
OK©GO TO 5.
NG©GO TO 4.
4 DETECT MALFUNCTIONING PART
Check the following.
IHarness connectors F22, M33 and M70, B50
IHarness for open or short between ECM and park/neutral position (PNP) switch
©Repair open circuit or short to ground or short to power in harness or connectors.
5 CHECK PARK/NEUTRAL POSITION (PNP) SWITCH
Refer to AT-115, ªDiagnostic Procedureº.
OK or NG
OK©GO TO 6.
NG©Replace park/neutral position (PNP) switch.
DTC P1706 PARK/NEUTRAL POSITION (PNP) SWITCH
Diagnostic Procedure
EC-608

DescriptionNBEC0596SYSTEM DESCRIPTIONNBEC0596S01
Sensor Input Signal to ECMECM func-
tionActuator
Mass air flow sensor Amount of intake air
VIAS con-
trolVIAS control solenoid valve Throttle position sensor Throttle position
Closed throttle position Throttle valve idle position
Ignition switch Start signal
Crankshaft position sensor (POS) Engine speed (POS signal)
Crankshaft position sensor (REF) Engine speed (REF signal)
Engine coolant temperature sensor Engine coolant temperature
SEF447Z
When the engine is running at low or medium speed, the power
valve is fully closed. Under this condition, the effective suction port
length is equivalent to the total length of the intake manifold collec-
tor's suction port including the intake valve. This long suction port
provides increased air intake which results in improved suction
efficiency and higher torque generation.
The surge tank and one-way valve are provided. When engine is
running at high speed, the ECM sends the signal to the VIAS con-
trol solenoid valve. This signal introduces the intake manifold
vacuum into the power valve actuator and therefore opens the
power valve to two suction passages together in the collector.
Under this condition, the effective port length is equivalent to the
length of the suction port provided independently for each cylinder.
This shortened port length results in enhanced engine output with
reduced suction resistance under high speeds.
VARIABLE INDUCTION AIR CONTROL SYSTEM (VIAS)
Description
EC-610

SEF018Z
COMPONENT DESCRIPTIONNBEC0596S02Power ValveNBEC0596S0201The power valve is installed in intake manifold collector and used
to control the suction passage of the variable induction air control
system. It is set in the fully closed or fully opened position by the
power valve actuator operated by the vacuum stored in the surge
tank. The vacuum in the surge tank is controlled by the VIAS con-
trol solenoid valve.
SEF019Z
VIAS Control Solenoid ValveNBEC0596S0202The VIAS control solenoid valve cuts the intake manifold vacuum
signal for power valve control. It responds to ON/OFF signals from
the ECM. When the solenoid is off, the vacuum signal from the
intake manifold is cut. When the ECM sends an ON signal the coil
pulls the plunger downward and feeds the vacuum signal to the
power valve actuator.
ECM Terminals and Reference ValueNBEC0684Specification data are reference values and are measured between each terminal and ground.
CAUTION:
Do not use ECM ground terminals when measuring input/output voltage. Doing so may result in dam-
age to the ECM's transistor. Use a ground other than ECM terminals, such as the ground.
TERMI-
NAL
NO.WIRE
COLORITEM CONDITION DATA (DC Voltage)
16 Y/GVIAS control solenoid
valve[Engine is running]
IIdle speedBATTERY VOLTAGE
(11 - 14V)
[Engine is running]
IEngine speed is above 5,000 rpm.0 - 1.0V
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VARIABLE INDUCTION AIR CONTROL SYSTEM (VIAS)
Description (Cont'd)
EC-611

Diagnostic ProcedureNBEC0598
1 CHECK OVERALL FUNCTION
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Perform ªVIAS SOL VALVEº in ªACTIVE TESTº mode with CONSULT-II.
3. Turn VIAS control solenoid valve ªONº and ªOFFº, and make sure that power valve actuator rod moves.
SEC304C
Without CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Rev engine quickly up to above 5,000 rpm and make sure that power valve actuator rod moves.
SEF021Z
OK or NG
OK©INSPECTION END
NG©GO TO 2.
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VARIABLE INDUCTION AIR CONTROL SYSTEM (VIAS)
Diagnostic Procedure
EC-613